<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style>
        .box {
            background-color: black;
        }
        .a,.b,.c,.d {
            width: 100px;
            height: 100px;
            margin-top: 10px;
        }
        .a {
            background-color: #1b6d85;
            float: left;
        }
        .b {
            background-color: #2b542c;
            float: left;
        }
        .c {
            background-color: #2e6da4;

            float: left;
        }
        .d {
            background-color: red;

            float: left;
        }
    </style>
</head>
<body>

<div class="box">
    <div class="a">a</div>
    <div class="b">b</div>
    <div class="c">c</div>
    <div class="d">d</div>
    你好
</div>
</body>
</html>